The Patent Document 1 discloses the relevant seat for automobile. This related invention is one that is equipped with a wire that is provided nearly horizontally at a seat back frame and an engaging portion that is provided at a back board for engaging with the wire. The wire has left and right arm portions that are nearly parallel to each other at both ends of a straight portion. The engaging portion of the back board is formed to be capable of being mounted on the straight portion of the wire, and capable of engaging with the arm portions of the wire by utilizing its own elastic deformation.